Touchback was absolutely the correct call. In college, if you muff a punt and recover it in the endzone, it is a touchback. The punt was muffed, he re-gained control in the EZ, fell down while not out of the EZ, ground caused a fumble that a BU player recovered (the BU player could have advanced the fumble had the Texas player not been down, as the fumble occurred after the muffed punt was controlled, therefore not a return of a muffed punt but a return of a fumble).